Technical Field
The present disclosure generally relates to various devices and approaches to perform intervertebral discectomy and implant and, more particularly, to a modular intervertebral spacer assembly, a hinged disc shaver assembly, a poly-sensor dilator, and a retroperitoneal retropsoas approach to perform anterior arthrodesis from a traditional prone position.
Description of the Related Art
Spinal disease such as spinal deformity or degeneration is a major cause of disability and pain in the human population, particularly among aging persons and persons who have suffered traumatic spinal injuries. Multiple conditions cause pain by compression of nerve roots. For example, sagittal imbalance, coronal imbalance, rotational imbalance, or other conditions can lead to failure of spinal integrity and associated pain and disability.
When the integrity of the spine fails, a traditional solution would be to perform arthrodesis of the spinal segments. Many spinal implant systems and spinal approaches have been developed to deal with this. One procedure which remains a mainstay for dealing with the failing spine is intervertebral arthrodesis and posterior elements supplementation. For example, the most common spine surgery is lumbar disc surgery in which the subject is most commonly positioned in the prone position.
Intervertebral arthrodesis is typically accomplished by removing the disc between vertebral bodies. Next, an intervertebral spacer is implanted in the vacated disc space. The intervertebral spacer provides structural integrity between the vertebra and allows for arthrodesis, or bony fusion, to occur for long term correction of the spine disease. Supplemental implants may be placed on/in the posterior elements for additional structural support while arthrodesis occurs.
With the introduction of fluoroscopy, microscopy and endoscopy to lumbar spine surgery, the size of incisions has decreased, along with the degree of soft tissue dissection required to approach surgical targets. This is invariably coupled with a decrease in visual field when compared to open surgery, and is a major barrier when transitioning open access surgeons to minimally invasive surgery. The philosophy of minimally invasive surgery (MIS) is maximizing clinical outcomes, while minimizing trauma to surrounding tissue, to achieve the same clinical result as open procedures.
Traditional prone position for spinal fusion allows access to the nerve roots directly but is limited by the small “footprint” that is allowed for arthrodesis. In particular, posterior approaches to the spine for posterior arthrodesis traverse the spinal canal, juxtapose the dura and exiting nerve roots, require retraction of the dura, and only permit implantation of spacers that are quite small compared to the actual disc space.
Common posterior approaches include Posterior Lumbar Intervertebral Fusion (PLIF) and transforaminal lumbar intervertebral fusion (TLIF). These approaches have the advantage of being performed with the subject in the most familiar positioning during surgery: the prone position. However the disadvantage is that such approaches do not allow for placement of larger, more robust implants for arthrodesis.
These disadvantages have led to anterior arthrodesis approaches. One advantage of anterior arthrodesis approaches is the ability to insert an implant with a much larger surface area for arthrodesis relative to posterior approaches. However these anterior methods are limited in the direct decompression of neural elements. In addition, these techniques require the subject to be supine or lateral decubitus position, which is unfamiliar for most spine surgeons, thereby requiring an access surgeon, whom is not always available. Further, if there is a need for posterior element instrumentation, which is often the case, then a second surgery or second position is required to achieve complete surgical intervention.
Common anterior approaches include the anterior lumbar intervertebral fusion and the extreme lateral intervertebral fusion (XLIF). Anterior arthrodesis approaches traditionally require an approach surgeon to reach the retroperitoneal space, prior to preparing the disc space for receiving implant. For example, XLIF requires traversing the retroperitoneal space in the decubitus position, a non-traditional position for spine surgeons. XLIF approaches also require traversing through the psoas muscle, where the lumbar plexus is intimately embedded.
Thus, more creative surgical approaches, such as Axial Lateral intervertebral fusion (AxialLIF) and XLIF, lack the familiarity in positioning or anatomical approaches to gain proficiency quickly and avoid unintended complications. The need for access surgeons for procedures such as ALIF, XLIF, or thorascopy often limit the procedure's ubiquity.
Furthermore, a significant limitation of current retroperitoneal approaches is that they are performed with the subject in the lateral decubitus position, requiring the surgeon to traverse a space that spine surgeons are not traditionally familiar with, and where frequently debated complications may occur. Many of the problems associated with approaches in which the subject is in the lateral decubitus position arise from the proximity of the vital structures such as the ureters, aorta, inferior vena cava, etc., in the surgical field.
Direct lateral transpsoas approaches have been described since the early 2000's for intervertebral fusion, including the XLIF and direct lateral fusion (DLIF) approaches. However, significant controversy about the safety of direct lateral transpsoas approach remains, despite industry efforts for surgeon education.